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PARMACOLOGY

Assignment Miosis, Mydriasis and Cyclople gia.

Submitted to:
Dr Iradat

. Visceromotor nerve axons (which constitute a portion of the III cranial nerve. carried through the optic nerve (cranial nerve II) to the brain. and through the retinal photoceptors is converted into an electric impulse. Pancoast tumor (a tumor of the apical lung).
Causes:
Age The suffering of miosis increases with age. where it connects to the pretectal nucleus of the high midbrain. Antipsychotics. It bypasses the lateral geniculate nucleus and the primary visual cortex. including haloperidol. This occurs because sympathetic activity from the ciliary ganglion is lost thus parasympathetics are not inhibited. codeine. heroin and methadone . whose parasympathetic axons innervate the constrictor muscle of the iris. along with the somatomotor portion derived from the Edinger-Westphal nucleus) synapse on ciliary ganglion neurons. quetiapine and others. olanzapine. due to damage to the ascending sympathetic tract that would normally cause the pupil to dilate. Diseases • • • Horner syndrome (a set of abnormalities in the nervous supply of the face due to damage to the sympathetic nervous system). thorazine. producing miosis.Miosis:
“Reflex contraction of the sphincter muscle of the iris in response to a bright light (or certain drugs) causing the pupil to become smaller” “Constriction of the pupil to a diameter of less than two millimeters”
Physiology Of The Photomotor Reflex:
Visual stimuli enters the eye. From the pretectal nucleus neurons send axons to neurons of the Edinger-Westphal nucleus whose visceromotor axons run along both the left and right oculomotor nerves. morphine. Hemorrhage into pons (intracranial hemorrhage)
Drugs • • Opioids such as tramadol.

The mechanism of mydriasis depends on the agent being used.• • • • • •
Cholinergic agents such as those used to treat Alzheimer's disease and nerve gases. composed of circularly arranged muscle fibers. composed of radially arranged muscle fibers. a noradrenergic and specific serotonergic antidepressant (NaSSA) Trazodone. Sympathetic stimulation of α1 adrenergic receptors causes the contraction of the radial muscle. the dilator acts to pull the iris outward. cholinergic drugs such as carbachol (Miostat) and neostigmine. a muscular sheath that radiates outward like the spokes of a wheel from the center of the iris around the pupil. Conversely. and subsequent dilation of the pupil. and the iris dilator. Some cancer chemotherapy drugs. the latter by the sympathetic nervous system. when exposed to mustard gas. Mirtazapine. or over activity of the sympathetic nervous system. Some MAO Inhibitors.
.
Mydriasis:
 “Dilation of the pupil of the eye caused by contraction of the dilator muscle of the iris. With a decrease in light or the pharmacologic action of certain drugs.
1. In some rare cases. Miotics
A miotic substance causes the constriction of the pupil of the eye (or miosis). parasympathetic stimulation causes contraction of the circular muscle and constriction of the pupil. The former is innervated by the parasympathetic nervous system. It usually involves either a disruption of the parasympathetic nerve supply to the eye (which causes contraction of the pupil). including camptothecin derivatives. enlarging the pupil”  “The condition of an eye having an abnormally large pupil diameter (5 mm in daylight)”
Mechanism:
There are two types of muscle that control the size of the iris: the iris sphincter.

and scopolamine b) Hallucinogens such as LSD. psilocybin. or miosis. epilepsy.Causes:
Natural release of the hormone oxytocin can cause mild to moderate mydriasis. remains unaffected. the iris sphincter (the muscle responsible for closing the pupil) or the nerves controlling it can be damaged. Damage to this nerve typically manifests itself as mydriasis. Scopolamine and Murocol-2. the oculomotor nerve. h) Opioid rebound and withdrawal. d) Cocaine. and mescaline.g. o Autonomic Neuropathy: The parasympathetic nervous supply. hyoscyamine.
Cycloplegia:
“Paralysis of the ciliary muscles of the eye that results in the loss of visual accommodation”
. which causes constriction of the pupil. because the sympathetic supply to the pupil. is supplied by cranial nerve III.
Treatment:
The most common drugs that are used to treat Mydriasis are Phenylephrine. which causes mydriasis. c) Drugs that increase overall serotonin levels in general are capable of causing mydriasis. Multiple central nervous system disorders e. e) Amphetamines. reducing or eliminating consensual reactivity to light. o Strong sexual arousal can often lead to very enlarged pupils.

Mydriatics: A mydriatic is an agent that induces dilation of the pupil. and therefore unopposed. f) Antidepressants.
o
a) Anticholinergics such as atropine. o Traumatic: In cases of head injury or orbit trauma (eye injury). g) Antihistamines. stroke are known to lead to temporal mydriasis as well.

Causes:
• • Toxic or traumatic conditions. This is often associated with the related condition of iridoplegia . The strongest cycloplegic drug is atropine. syphilis. debilitating illness. Other cycloplegic drugs are hyoscine hydrobromide(scopolamine). diphtheria. influenza.
. duhoisine sulphate. hyoscyamine sulphate. They are indicated for use in cycloplegic refraction (to paralyze the ciliary muscle in order to determine the true refractive error of the lens) and the treatment of uveitis.g.
Consequencies:
One important consequence of cycloplegia is the inability to focus (that is to change the shape of the lens) of the affected eye. It has been suggested that it is most suitable drug for children.
Cycloplegic drugs:
Cycloplegic drugs are generally muscarinic receptor blockers. paralysis of the third nerve. The drug methylatropine nitrate (Metropine) has the same cycloplegic effects as that of atropine with less mydriasis and there is a quicker recovery. cerebral disease etc. diabetes.which is paralysis of the iris and results in fixed pupil size (known technically as "mydriasis"). contusion of the ciliary muscle. Nervous diseases e.